1. Description of Related Art
One of the main problems with docks used for marine pleasure craft in climates which have cold winters is ice-related damage to the docks. A number of different ice damage problems occur, including crushing and buckling of docks due to wind-rows, that is, ice which is piled up near the shoreline by action of waves and/or wind. In rivers and other bodies of water subject to currents, such as tidal currents, moving ice floes can knock down, sever or otherwise damage docks and their pilings. A lesser known but very real problem is the lifting of pilings caused by extensive formation of ice rings on exposed pilings at the waterline on account of swells or other gentle wave action. This occurs in situations where the air temperature is below freezing and water cyclically laps upon and freezes to a dock piling. When this process continues long enough, a large ring of ice forms on the piling, which, when of sufficient size and buoyancy, will lift the piling up at least partially out of the river or lake bottom into which the piling has been driven.
A number of remedies are known to avoid one or more forms of the above-mentioned ice damage. These include: (1) the heavy reinforcement of a dock to the extent that the ice is generally not capable of damaging the dock; (2) the partial or complete removal of docks from the water; and (3) the installation of air bubblers. The first option is inordinately expensive, and often aesthetically unacceptable. It is also sometimes environmentally unacceptable in locations where a large solid structure jutting out in the water causes formation of sandbars or other undesired changes, to the adjacent shoreline or lake bottom due to modified wave or current action.
The removal of a dock from the water is also not completely acceptable in many instances. First, the removal of a dock from and reinstallation of a dock into a body of water can be expensive and/or time-consuming. Removing the deck while leaving the dock pilings in place is one alternative. This however does not stop the formation of ice rings which yank the pilings up from the lake bottom, and re-sinking the pilings is expensive and time-consuming.
In my earlier patent, U.S. Pat. No. 4,123,912 entitled "Lightweight Demountable Dock Assembly," granted Nov. 7, 1978, there is disclosed an improved lightweight dock assembly designed for partial removal. It has a mainspan and a ramp extending from the shore. The mainspan is removable, and supported by vertical members near the shore and a tripod structure away from shore. After removal of the mainspan and its ramp, the support structure and tripod may be rotated at their footings for underwater storage. The mainspan is designed to be lightweight. Nevertheless, its removal or reinstallation is a significant chore that requires at least two men preferably with a boat, or a crane to support the mainspan during its removal and reinstallation. Further, the removal and reinstallation of the dock is typically done when conditions are least favorable, i.e., in the fall and spring when the water is cold and the winds are often high. Also, once removed, the deck or other sections of the dock must be stored, which can present storage space problems and is unattractive. The removal and storage of a dock out of water may also hasten deterioration in that the once-submerged portions of the dock by exposure to different weathering conditions.
The other alternative for protecting docks against ice damage is the use of air bubblers to prevent ice from freezing around a dock. However, bubblers are subject to power failures, and present the hazard of open water in the winter time. Also, bubblers are ineffective against ice damage due to ice pile-ups caused by heavy wind or wave action, or by ice being carried by currents.
In light of the foregoing problems, it is a principal object of the present invention to provide a dock system which is substantially immune to ice damage and can be used year after year. It is a related object of the present invention to provide an economical submersible dock system which resists ice damage by being lowered to the bottom of a body of water for storage during the winter in a substantially fully assembled state, and can be easily retrieved when the ice is gone. It is still another object of the present invention to provide a submersible dock system which is easy to manufacture, install, and to lower and raise.
It is another object of the present invention to provide a submersible dock system which employs several independently adjustable leveling pad assemblies for supporting the dock so its deck remains horizontal over time without resort to pilings or other anchoring means which need be driven into the ground below the water.
It is yet another object of the present invention to provide a submersible dock system which is made up of many substantially identical parts, for economy of manufacture, and which can be adjusted at installation for different size boats.
It is still another object to provide a strong, lightweight submersible dock system made of economically priced steel with at least three corrosion protection mechanisms for allowing its components to survive fifteen or twenty years in a water environment without significant deterioration.